说明：不同温度下趋磁细菌群落的系统发育树（A）和群落相似性的主坐标分析（B），a、b和c表示同一温度下的三个平行样品。从图中可以看出，37°C下趋磁细菌的种群多样性与其余温度下的样品明显不同。
近日，国际杂志MicrobiologyOpen在线刊登了中科院地质与地球物理研究所研究人员的最新研究成果“Short-term effects of temperature on the abundance and diversity of magnetotactic cocci.，”，文章中，研究者发现生长温度影响趋磁细菌数量和种群多样性。
古温度是古环境重建的重要参数。已有研究表明，全球变暖对高等动植物的多样性具有显著影响，但是，温度变化对微生物有何影响目前尚不十分清楚。微生物分布广、数量大、多样性高，在全球元素循环和生态系统功能维持等方面发挥十分重要的作用，能否用微生物变化反映环境温度是一个非常值得研究的科学问题。
趋磁细菌是一类能沿地磁场磁力线方向运动的微生物的总称，它们在体内合成磁铁矿 (Fe3O4) 或胶黄铁矿 (Fe3S4) 磁小体，多呈链状排列。这类细菌在自然界分布十分广泛、易于磁收集且多样性适中，可以作为研究微生物响应气候和环境变化的理想模式生物类群。
中科院地质与地球物理研究所地球深部结构与过程研究室古地磁与年代学实验室、中-法生物矿化与纳米结构联合实验室林巍博士及其合作导师潘永信研究员等通过实验室模拟研究，揭示了温度变化对趋磁细菌数量和种群多样性的影响。他们将相同来源的沉积物样品在实验室置于不同温度下，保存约一个月后发现，9-26°C样品中趋磁细菌的群落结构非常相似，而37°C下趋磁细菌的多样性有明显差异，样品中趋磁细菌的数量也显著降低，这表明温度升高可以显著影响趋磁细菌数量及其种群多样性。
这项研究意义在于，可以利用沉积物中趋磁细菌古DNA信息反映其种群多样性，作为古温度估计的约束。有报道称趋磁细菌合成磁小体磁铁矿晶体的氧同位素比值也能反映细菌生长环境的温度。因此，趋磁细菌及磁小体在古环境研究中具有潜力。
本研究工作得到中国科学院和国家自然科学基金资助。（生物谷Bioon.com）
doi:10.1002/mbo3.7
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Short-term effects of temperature on the abundance and diversity of magnetotactic cocci
Wei Lin1,2,*, Yinzhao Wang1,2, Yongxin Pan1,2
Temperature is one of the most important climate factors that can regulate the activity and growth of organisms. However, it is so far unclear how temperature influences the abundance and community composition of magnetotactic bacteria (MTB) that mineralize intracellular magnetite and/or greigite magnetosomes and play significant roles in the global iron cycling and sediment magnetization. To address this specific problem, in this study we have assessed the impact of temperature on freshwater magnetotactic cocci through laboratory microcosm simulations. Microcosms containing MTB were exposed to four constant temperatures ranging from 9°C to 37°C. After 10 days and 28 days of incubation, no significant differences in abundance were detected in microcosms at 9°C, 15°C, and 26°C (Student's t-test, P > 0.05); however, microcosms exposed to 37°C exhibited a significant decrease of magnetotactic cocci abundance (P < 0.05). Dendrogram analysis of community-amplified ribosomal DNA restriction analysis (community ARDRA) banding patterns distinguished the 37°C samples from samples at lower temperatures regardless of incubation periods. Furthermore, clone library analysis revealed that most of the operational taxonomic units (OTUs) detected in samples from 9°C to 26°C were absent from the 37°C microcosms, whereas six OTUs were exclusively detected in the 37°C samples. Community compositions from four incubation temperatures were further compared using statistical phylogenetic methods (UniFrac and LIBSHUFF), which revealed that the 37°C samples harbored phylogenetically distinct MTB communities compared to those found in 9°C, 15°C, and 26°C samples. Taken together, our results indicate that elevated temperature can influence the abundance and diversity of dominant members of magnetotactic cocci. This linkage further infers that the abundance and diversity of MTB (e.g., based on the fossil magnetosomes) may be useful in reconstruction of paleotemperature.
